CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (Unaudited) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Operating Activities:
Net Income	$ 101.4	$ 92.6
Adjustments to reconcile net income to cash provided by operations:
Depreciation and amortization	66.8	63.7
Amortization of deferred costs	1.3	1.2
Asset impairment	0.1	4.2
Net gain on sale of operating assets	0	(3.6)
Changes in operating assets and liabilities:
Trade and other receivables	1.5	7.8
Gas receivables and storage assets	6.8	1.7
Costs recoverable from customers	0.9	2.2
Other assets	2.4	1.7
Trade and other payables	(18.2)	(2.4)
Other payables, affiliates	0.7	0
Gas payables	4.8	(1.5)
Accrued liabilities	(31.1)	(39.8)
Other liabilities	(8.1)	(18.0)
Net cash provided by operating activities	129.3	109.8
Investing Activities:
Capital expenditures	(70.6)	(26.0)
Proceeds from sale of operating assets	1.0	1.7
Proceeds from insurance and other recoveries	1.4	0.4
Net cash used in investing activities	(68.2)	(23.9)
Financing Activities:
Proceeds from borrowings on revolving credit agreement	263.0	370.0
Repayment of borrowings on revolving credit agreement	(195.0)	(330.0)
Advances from affiliate	(0.4)	4.7
Repayment of contribution received related to predecessor equity	0	(284.8)
Distributions paid	(128.3)	(114.0)
Proceeds from sale of common units	0	245.0
Capital contribution from general partner	0	5.2
Net cash used in financing activities	(60.7)	(103.9)
Increase (decrease) in cash and cash equivalents	0.4	(18.0)
Cash and cash equivalents at beginning of period	3.9	21.9
Cash and cash equivalents at end of period	$ 4.3	$ 3.9